An internal combustion engine installed to a vehicle is equipped with an EGR device which returns a part of an exhaust gas to an intake passage as an EGR gas with an aim of enhancing fuel efficiency and reducing knocking and an emission of an exhaust gas. However, when an EGR gas with a high water content is returned to the intake passage, condensate water may be produced when an intake gas, which is a mixture of the EGR gas and intake air (fresh air), is cooled in an intercooler. The condensate water possibly gives rise to a corrosion of a metal part.
A technique of restricting production of condensate water in the intercooler is described in, for example, Patent Literature 1. According to the disclosed technique, a coolant circuit circulating a coolant through an intercooler and an EGR cooler is provided, and condensate water is forcedly produced by cooling an EGR gas in the EGR cooler. The condensate water is collected into a trap portion to dehumidify the EGR gas. The EGR gas is then heated in an EGR heater to lower a relative humidity and returned to an intake passage.